2. Dr. Edmond Locard (1877–1966)
In early 20th century, he formulated the basic principle that “every contact leaves a trace.”

3. Locard’s Principle Principle of Exchange
Part 1: when a person comes into contact with an object or another person, a cross transfer of physical evidence can occur

4. Locard’s Principle
Part 2: the intensity, duration and type of weapon determine the extent of transfer

5. Types of Evidence Circumstantial: indirect evidence Direct-
NOT witnessed
- may link a suspect and a crime scene
ex. Suspect’s gun found at crime scene
Circumstantial: indirect evidence
Direct
firsthand observations:
- eyewitness accounts
dashboard video cameras
confessions

6. What will evidence collected at a scene do for the investigation?
Types of Evidence
Testimonial evidence includes oral or written statements given to police as well as court testimony by people who witnessed an event.
(Physical-weapon, bullets, clothing)
(Biological- from living, blood, grass)
Trace evidence refers to physical evidence that is found in small but measurable amounts, such as strands of hair, fibers, or skin cells.
What will evidence collected at a scene do for the investigation?
May prove that a crime has been committed
Establish key elements of a crime
Link a suspect with a crime scene or a victim
Establish the identity of a victim or suspect
Corroborate verbal witness testimony
Exonerate the innocent.
Give detectives leads to work with in the case
Source:

7. Trace evidence: TINY Pet hair on clothes or rugs Hair on brush
Fingerprints on glass
Soil tracked inside on shoes
Drop of blood on t shirt
A used facial tissue
Paint chips
Broken glass
Fiber from clothing

8. Individual evidence: single person -DNA, fingerprint
Class evidence: narrows the identity to a group
ex. Blood type ABO, color of…
Shoe size

9. Class Discussion Casey Anthony – new use of Air Sample
Coverage of Casey Anthony Murder Trial
OJ Simpson – “If the glove doesn’t fit, then you must acquit”
OJ Simpson Trial Criminal Evidence
Suggested STOP of Day 1

10. End Part 1

11. CSI Team: Police Officers: usually first responder
Crime Scene Investigators: document crime and collect physical evidence
Recorder
Sketch artist
Photographers
Evidence collectors
Medical Examiners: coroners may be necessary to determine cause of death in a homicide case
Detectives: look for leads, interview witnesses and talking to the CSI about evidence
Specialists: entomologists, psychologists,anthropologist, toxicologist, ballistics,

12. Securing and Collecting the Evidence
Must be properly packaged, sealed and labeled
Specific procedures must be followed for collection and storage
Liquids and arson remains: airtight, unbreakable container
Biological evidence: breathable containers to reduce mold

13. Securing and Collecting the Evidence
After evidence is allowed to dry, it is then packaged into a paper bindle
Paper bindle (druggist fold) then placed in paper or plastic container
Outer container then sealed with tape and signed by the collector on the label

14. Evidence log and Chain of Custody document is attached to the evidence container.
Contains:
Case number
Item inventory number
Description of the evidence
Date and Time of recovery
Signature of person recovering evidence
Signature of any witnesses present during collection
Optional for reference evidence (evidence collected from a known person):
Name of suspect
Name of victim

15. Chain of Custody Form Example

16. CHAIN OF CUSTODY: Must be maintained to secure evidence
Collector finds evidence and bags it in appropriate container
The final container is the collection bag labeled with pertinent information
Collection bag is sealed and collector’s signature written across sealed edge of the container
Then the evidence is taken to evidence storage and logged
Not all evidence collected gets tested. Once the necessary tests are determined, then the evidence is checked out and sent to a lab

17. CHAIN OF CUSTODY: Must be maintained to secure evidence
After evidence has been received by the Laboratory:
Tech opens bag (tears) somewhere that isn’t over someone else’s evidence seal
Technician handles evidence then repackages evidence in original packaging and then seals in new packaging
Sign chain of custody log
Ensures responsible handling from crime scene to courtroom and vice versa

18. Analyze Evidence
FBI crime is largest forensics lab in the world. They:
Process all evidence to determine facts of the case
Each technician has one specialty (one type of evidence). See next slide.
Lab results sent to lead detective
Test results lead to crime scene reconstruction
Detective takes evidence and tries fit into scenario
Analysis can link a suspect to scene or victim or lead to acquittal
Direct evidence is more compelling than circumstantial

19. Investigating the Evidence
Forensic Science disciplines at the Illinois State Police Crime Labs
Drug Chemistry – Determines the presence of controlled substances and the identification of marijuana
Trace Chemistry - Identification and comparison of materials from fires, explosions, paints, and glass.
Microscopy – Microscopic identification and comparison of evidence, such as hairs, fibers, woods, soils, building materials, insulation and other materials.
Biology/DNA – Analysis of body fluids and dried stains such as blood, semen, and saliva.
Toxicology – Tests body fluids and tissues to determine the presence of drugs and poisons.
Latent Prints - Identification and comparison of fingerprints or other hidden impressions from sources like feet, shoes, ears, lips or the tread on vehicle tires.
Ballistics (Firearms) – Study of bullets and ammunition through the comparison of fired bullets, cartridges, guns, and gunpowder patterns on people and objects.
Toolmarks – Examines marks left by tools on objects at a crime scene or on a victim, such as a hammer used to break a door or a screwdriver used to pick a lock.
Questioned Documents - Examination of documents to compare handwriting, ink, paper, writing instruments, printers, and other characteristics that would help to identify its origin.
Suggested STOP of Day 2
Source:

20. National databases available to Forensic Scientists
List of Forensic Databases from NIJ Journal No. 258, October 2007
On your own sheet of paper, create a table listing the different databases available and a brief description of each

21. Crime Scene Reconstruction
Hypothetical sequence of events
Examine evidence and compare to witness accounts to determine reliability
Evidence does not lie but it can be staged

22. Staged Crime Scenes Unique problem: evidence does not match testimony
Common situations:
Arson: stage fire to cover rubbery, murder
Suicide/murder: death may be alcohol or overdose
Burglary: staged to collect money

23. Things to consider when determining if staging occurred:
Initially treat all death investigations as homicide, however:
Do the type(s) of wounds found on the victim match the weapon employed?
Could the wounds be easily self inflicted?
Establish a profile of the victim through interviews with friends and family
Evaluate the behavior ( mood and actions) of the victim before the event
Evaluate the behavior ( mood and actions) of any suspects before the event
Corroborate statements with evidential facts
Reconstruct the event
Conduct all forensic examinations to determine the facts of the case

24. SUMMARY Locard’s principle
Evidence may be direct: eyewitness or Circumstantial: does not directly prove a fact
Evidence can be physical or biological (trace can be either)
CSI team: police officers, detectives, CSI investigators, medical examiners and specialists
CS investigation: recognizing, documenting and collecting evidence from a scene
First responding officer: id extent of crime scene (including 1 and 2), secure the scene and segregate witnesses
walk the scene, id evidence then document scene by photos and sketches
Evidence must be properly handled, collected and labeled to maintain Chain of Custody
Evidence is analyzed in a forensic lab, results provided to detectives who fit results into crime scenario

25. What evidence would you collect?
Mock Crime Scene:
Mock Crime Scene: